1. Field of the Invention
The present invention relates to chip package structures and methods for forming the chip package structures, and, more particularly, to a package structure for a micro-electro-mechanical system.
2. Description of Related Art
It is the trend to develop a chip package structure with small volume and high performance. There are various types of chip package structures, such as opto electronic devices, micro-electro-mechanical system (MEMS) or sensors.
As shown in FIG. 1, a chip package structure 1 for a micro-electro-mechanical system includes a chip 10 having a sensing device 11 thereon, and a silicon cover 12 having an inner protruding portion and coupled to the chip 10 for covering the sensing device 11. The sensing device 11 has an inertial object 110 having a corresponding protruding portion 120, and an elastic component 111 connected to the inertial object 110 and the chip 10.
While the elastic component 111 moves the inertial object 110 along a linear direction (such as horizontal direction), the vibration of the inertial object 110 along another direction (such as a vertical direction) is limited by the protruding portion 120 to be within an acceptable range, so as to prevent the inertial object 110 from leaving a predetermined path.
However, the conventional silicon cover 12 is provided or made by a wafer fabrication factory, such that the silicon cover 12 is made of inorganic materials, and the protruding portion is made by etching. The etching process includes multiple steps such that the fabrication of the silicon cover 12 takes long time, needs various materials (such as etching solution, resist layer) and thus has high cost.